2.0 Analysis 2.1 General Sixty minutes had elapsed between the time the oceanic planner determined that FL330 was an appropriate altitude for BAW92X and the time of the occurrence. There were four opportunities for individual controllers to detect the conflict and correct it. Normally, aircraft separation, conflict detection, and conflict correction take place routinely, regardless of the traffic volume. 2.2 Traffic Volume During the late afternoon, the traffic activity that normally follows the daily westbound flow is at its lowest. Changeover in the main-flow direction will take place over the next few hours and the controller evening shift changes are also taking place. Controllers arrive at their positions anticipating few traffic problems, knowing that the main traffic volume will occur later in the evening. Relieving controllers anticipate that the controllers being relieved will have already resolved any potential traffic conflicts or will point out unresolved traffic conflicts for their immediate attention. Considering the conditions that normally exist, the first few hours of the evening shift are the least demanding of the shift. This established routine can engender a complacent attitude, causing a lack of vigilance and leading to a loss of controller situational awareness. 2.3 Traffic Conflict Detection 2.3.1 Oceanic Planner If the oceanic planner had completed an adequate check of the ocean board, he might have detected the presence of DAL49 already over the ocean at FL330. In that case, he would not have planned BAW92X at the same altitude. Rather than checking the ocean data board himself, a more appropriate action for the oceanic planner might have been to interrupt the ocean controller and his trainee, or wait for an opportune moment, and discuss the altitude for BAW92X with him. The ocean controller, being more familiar with the traffic in his sector, might have been able to detect the conflict more easily than the planner. 2.3.2 High-Level Domestic Controller When the high-level domestic controller received the flight data strip for BAW92X and placed it with the strip for DAL49 on the data board, he did not notice that both aircraft were at the same altitude. He did not detect the traffic conflict during the period that both strips were on his sector's data board. Given that the two differently coloured strips were the only two under the St. Anthony fix designator, it is likely that the high-level domestic controller's routine data board scan was ineffective. 2.3.3 High-Level Domestic OJI and Trainee Although the controllers reported that a briefing was completed when the OJI and his trainee relieved the first high-level controller, the briefing did not include any information about the conflict between DAL49 and BAW92X. The data board checks performed by both the OJI and the trainee were ineffective, as neither detected the conflict at that time. The trainee controller's mental picture of the air traffic and his situational awareness were inadequate. This is highlighted by his action of twice marking flight progress information on BAW92X's black data strip and failing to detect the traffic conflict, even though DAL49's red strip was the only other strip under the St. Anthony fix designator. The section of domestic airspace where the occurrence took place does not have radar coverage. Even if radar coverage were available in this area, though, it is unlikely that the controllers would have detected the conflict, because the radar was centred to display the traffic on the tracks in the southern part of the airspace. When the controllers detected the traffic conflict, they cleared DAL49 to climb without instructing the pilot to expedite, and they did not give a traffic advisory about BAW92X's position. It is possible that the actual air traffic picture deviated so greatly from the mental picture they had already developed that they did not give the most appropriate instructions to DAL49. 2.3.4 Oceanic Controller If the controller who relieved the oceanic sector prior to the occurrence had done an adequate data board check, he would have detected the traffic conflict. When the oceanic controller received the second data strip for BAW92X with the speed change, he saw that it was not a routing change, assumed that the route was already free of traffic conflict, and did not check it against the other strips on the ocean data board. The oceanic controller did not detect the conflict during his routine scan of the ocean data board either. 2.4 Controller Situational Awareness It is likely that the failure of the involved controllers to maintain their situational awareness was due to the development of a complacent attitude during a period of low traffic activity. Contributing to this complacent attitude was a reliance on automated systems, such as GAATS, and other controllers to detect potential traffic conflicts. This complacent attitude led to a lack of vigilance and less compliance with established procedures and checklists. When a traffic conflict does develop during a period of low traffic activity, as occurred on this occasion, it is less likely to be detected than it would be during a period of peak traffic activity. Adherence to established procedures and the use of written checklists by the controllers would likely have resulted in earlier detection and resolution of the conflict, and would have reduced the risk of collision. 2.5 Traffic Alert and Collision Avoidance System The crew of DAL49 decided to expedite the climb to FL350 after the first officer observed conflicting opposite-direction traffic at 30 miles on the TCAS. This decision was based solely on the TCAS information and resulted in the two aircraft achieving 1,800 feet vertical separation when they passed. Without an ATC instruction to expedite the climb and without the information provided by TCAS, the crew of DAL49 probably would have performed a slower en route climb, resulting in less vertical separation with BAW92X when they passed. 3.0 Conclusions 3.1 Findings All the controllers involved in this occurrence were qualified and current at their positions. All equipment available to the controllers was serviceable and being used. Staffing in the Gander Area Control Centre met unit standards. The traffic volume was assessed as light to moderate with normal complexity. The oceanic planner did not detect a traffic conflict with DAL49 when he planned the altitude for BAW92X. The first high-level domestic controller occupying the sector did not detect the traffic conflict between the two aircraft. The OJI and high-level domestic radar trainee who relieved the sector did not detect the traffic conflict between the two aircraft. The oceanic controller who occupied the ocean sector during the time prior to the occurrence did not detect the traffic conflict. When the risk of collision was detected, DAL49 was not instructed to expedite the climb to FL350, and no traffic information was passed. The crew of DAL49 decided to expedite their climb based on TCAS information about opposite direction traffic. DAL49 passed about 1,800 feet above and one mile south of BAW92X. Established procedures and written checklists for flight data board scans and sector briefings were not effectively followed. 3.2 Causes The controllers involved in this occurrence did not detect the traffic conflict between DAL49 and BAW92X prior to the risk of collision. Contributing to this occurrence were the controllers' loss of situational awareness created by complacency and a lack of vigilance during a period of low traffic activity. 4.0 Safety Action 4.1 Action Taken 4.1.1 Transport Canada Previous TSB investigations have shown that controller inattention, lack of vigilance, or loss of situational awareness are major factors in loss of separation occurrences. Therefore, subsequent to a risk of collision between two A320 Airbus aircraft in December 1993 (A93C0208), the Board recommended that: The Department of Transport sponsor research into methods for maintaining reliable controller vigilance in an increasingly automated ATC work environment. In response, Transport Canada (TC) indicated that research would be conducted on the most effective communication, focusing, and distraction-control techniques for air traffic controllers, and relevant training programs would be implemented. Additionally, TC has started research into other areas that affect controller vigilance and into programs designed to optimize controller health and performance. To address the issue of controller situational awareness in the short term, the Board recommended that: The Department of Transport provide training for Canadian controllers similar to crew resource management (CRM) training for pilots. In response, TC indicated its intention to develop a decision making course for controllers (similar to the pilot decision making (PDM) courses) which would include a discussion of the various factors that affect situational awareness.